1. Field of the Invention
The present invention relates to wireless network communications. More particularly, the present invention relates to secure localization in wireless networks.
2. Description of the Related Art
Location schemes for wireless networks are typically based on the features of the underlying physical layer. For example, some traditional schemes have been based on ultrasound, infrared, Bluetooth, or 802.11 RF networks. These schemes infer the location of users by measuring various parameters such as received signal strength indicator (RSSI), time of flight, and angle of arrival. Some of these schemes are client based, that is, they rely on the client to determine its own location, while others are network based where the network infrastructure is used to determine location.
Traditional location schemes normally rely on measuring the signal strength (SS) parameter of transmitted signals. A SS map is determined that represents the SS at various locations. The system then tries to determine location based on the best match between observed signal strength and the SS map. In such systems, however, the emphasis is on localization while the presence of malicious users is neglected. Services in which location determination is a major component would attract the attention of adversaries whose goal would be to try to deceive the location system.
Global Positioning System (GPS) is currently a popular location technology. GPS relies upon a GPS receiver (client) to compute location using received satellite signals. The location is then reported to any interested systems. Such a process, however, is prone to compromise in that malicious end users can provide incorrect location reports, thus deceiving the system. When using GPS-based location systems, it is therefore necessary to investigate and employ alternative technologies for determining location securely.
One solution for secure location determination is to use the time-of-flight technique. In the time-of-flight technique, each end-user device is required to have equipment that can reflect back, that is, return, transmitted signals without any delay. Various techniques, such as verifiable multilateration, can then be combined with this basic idea to ensure that end users will not be able to falsify location. One problem with this approach, however, is the additional cost associated with the infrastructure necessary for implementation. Accordingly, what is needed is a localization system for operation over a network that provides location determination securely in a cost effective manner.